Turning brake controlling system for use in power shovel

ABSTRACT

A turning brake controlling system for use in power shovel arranged such that even when a microprocessor for controlling the operation of the turning brake actuator means malfunctions the turning brake can be applied without fail by shifting a turning lever to its neutral position, and the upper turning body can be stopped at a predetermined position without being subjected to the influence of external forces such as gravity, etc. when it is turned slowly on a slope. The turning brake controlling system has a turning lever signal transmitter (1) adapted to output a turning lever signal &#34;a&#34; when the turning lever is shifted from its turning position to its neutral position, and a turning brake actuating signal generator (2) adapted to receive the turning lever signal and output a turning brake actuating signal (h) to a turning brake actuator means (3).

This application is a continuation of application Ser. No. 696,276 filedMay 2, 1991, which in turn is a continuation of application Ser. No.445,631, filed Jan. 11, 1990, now abandoned.

TECHNICAL FIELD OF THE INVENTION

This invention relates to a turning brake controlling system for use ina power shovel having an excavating implement mounted on the vehiclebody thereof so that it can be turned.

BACKGROUND TECHNIQUE OF THE INVENTION

A turning brake controlling system for applying braking force on theupper turning body of a power shovel is arranged to be actuatedautomatically to apply braking force on the upper turning body when theturning brake is actuated intentionally by the operator of the powershovel or when the turning lever for turning the upper turning body isshifted to its neutral position in order to stop the turning of theupper turning body. The turning brake means is usually adapted to beactuated several seconds after the turning lever is shifted from its"turning" position to its "neutral" position, thereby preventing suddenstoppage of the upper turning body.

Since the delay time for the turning brake; that is; the time whichpasses from the shifting of the turning lever from its "turning"position to its "neutral" position until the actuation of the turningbrake controlling system is predetermined, in the case of turningoperations of the shovel on a slope, if positioning of the upper turningbody in the turning direction is made by turning it slowly, then theupper turning body is turned during the delay time for the turning brakeunder the influence of gravity and leakage of fluid from the hydraulicmotor so that it is difficult to stop it towards a target.

Further, in case the above-mentioned conventional turning brakecontrolling system is controlled by means of a microprocessor, if themicroprocessor fails to fulfill arithmetic function as programmed forsome cause such as noise or static electricity, etc., then the binaryON-OFF control signal becomes unstable, or only either ON output or OFFoutput can be developed. As a result, the controlling function of theturning brake controlling system is completely lost thus creating adangerous condition, so that the operator cannot help stopping theoperation.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentionedcircumstances, and has for its first object to provide a turning brakecontrolling system for use in a power shovel arranged such that evenwhen a microprocessor for controlling the operation of a turning brakeactuator means malfunctions the turning brake can be actuated severalseconds after the turning lever is shifted form its "turning" positionto its "neutral" position.

Further, the second object of the present invention is to provide aturning brake controlling system for use in a power shovel arranged suchthat when the turning speed of the upper turning body becomes lower thana predetermined value the turning brake can be actuated even if itoccurs during the delay time for the turning brake, thereby eliminatingfree movement or turning of the upper turning body by the force ofgravity, etc. during the delay time for the turning brake, and accuratepositioning of the upper turning body can be made in turning it slowlywhen the power shovel is on a slope.

Further, the third object of the present invention is to provide aturning brake controlling system for use in a power shovel arranged suchthat the delay time for the turning brake may be varied with the turningspeed of the upper turning body when the turning lever is shifted fromits turning position to its neutral position so that in case the turningspeed is slow the delay time for the turning brake is reduced, and inparticular in case of slow turning operations on a slope, when theturning lever is shifted from its turning position to its neutralposition, the upper turning body is prevented from turning freely underthe influence of external forces such as the force of gravity, etc..

To achieve the above-mentioned objects, according to the first aspect ofthe present invention, there is provided a turning brake controllingsystem for use in an upper turning body of a power shovel arranged toreceive, as an input thereof, a turning lever signal outputted by aturning lever signal transmitter when the turning lever is shifted fromits turning position to its neutral position and output a turning brakeactuating signal to a turning brake actuator means, comprising: amicroprocessor for outputting a turning brake actuating signal to theturning brake actuator means; a microprocessor monitoring means formonitoring the operation of the microprocessor; a hardware circuitconnected in parallel with the microprocessor and which fulfills afunction corresponding to the arithmetic function of the microprocessor;and a switching circuit for switching output of the microprocessor overto output of said hardware circuit in accordance with the actuation ofsaid microprocessor monitoring means.

To achieve the above-mentioned objects, according to the second aspectof the present invention, there is provided a turning brake controllingsystem for use in a power shovel, characterized in that themicroprocessor and/or hardware circuit as described in the first aspectincludes a turning speed detector means adapted to detect the turningspeed of the upper turning body when the turning lever is shifted fromits turning position to its neutral position and the subsequent speedsthereof and output a turning speed signal corresponding to the thusdetected turning speed; and a turning brake signal generator meansadapted to receive, as inputs thereof, the turning speed signaloutputted by the turning speed detector means and the turning leversignal outputted by the turning lever signal transmitter and output aturning brake signal to the turning brake actuator means.

To achieve the above-mentioned objects, according to the third aspect ofthe present invention, there is provided a turning brake controllingsystem for use in a power shovel, characterized in that the turningbrake signal generator means as described in the second aspect isarranged to output a turning brake signal when the turning speed signalbecomes less than a preset value.

To achieve the above-mentioned objects, according to the fourth aspectof the present invention, there is provided a turning brake controllingsystem for use in a power shovel, characterized in that the turningbrake signal generator means as described in the second aspect isarranged to output a turning brake signal in a delay time which ispreset in accordance with the value of the turning speed signal.

The above-mentioned and other objects, aspects and advantages of thepresent invention will become apparent to those skilled in the art bymaking reference to the following description and the accompanyingdrawings in which preferred embodiments incorporating the principles ofthe present invention are shown by way of examples only.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram schematically showing the principal parts of afirst embodiment of the present invention;

FIG. 2 is a block diagram schematically showing the principal parts of asecond embodiment of the present invention;

FIG. 3 is a block diagram schematically showing the principal parts of athird embodiment of the present invention; and

FIGS. 4 and 5 are timing diagrams for the embodiments as shown in FIGS.2 and 3, respectively.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention will now be described below by way of the first,second and third embodiments thereof with reference to the accompanyingdrawings.

In the first place, the first embodiment of the present invention willbe described with reference to FIG. 1.

In FIG. 1, reference numeral 1 denotes a turning lever signaltransmitter adapted to output or transmit a turning lever signal a whena turning lever, not shown, for operating the turning of an upperturning body (not shown) of a power shovel is shifted to its neutralposition.

Reference numeral 2 denotes a power shovel turning brake controllingsystem adapted to receive a turning lever signal a and output ortransmit a turning brake actuating signal to a turning brake actuatormeans 3. This turning brake controlling system 2 includes amicroprocessor 21 adapted to receive, as an input thereof, a turninglever signal a, and a delay circuit 22 serving as a hardware circuit.This delay circuit 22 fulfills a function which corresponds to thearithmetic function of the microprocessor 21.

Reference numeral 23 denotes a watchdog which serves as a monitoringmeans for the microprocessor 21 and which receives, as an input thereof,a signal c outputted by the microprocessor 21 which is either a normalsignal "1" or an abnormal signal "0". This microprocessor 21 is adaptedto be unreset when the signal d outputted by the watchdog 23 is a normalsignal "1", and reset when the signal is an abnormal signal "0".Further, the watchdog 23 is adapted to output a normal signal "1" whenthe signal c is a normal signal "1", and output an abnormal signal "0"when the signal c is an abnormal signal.

Reference numeral 24 denotes an AND circuit which receives, as an inputthereof, a signal b outputted by the microprocessor 21 and a signal doutputted by the watchdog 23 and which is adapted to output a signal fthat becomes a normal signal "1" only when the signals b and d arenormal signals "1".

Reference numeral 25 denotes a NOR circuit which receives at its inputside the output signal d from the watchdog 23 and an output signal efrom the delay circuit 22 and which is adapted to output a signal g.

Reference numeral 26 denotes an OR circuit which receives, at its inputside, output signals f and g from AND circuit 24 and NOR circuit 25,respectively, and which is adapted to transmit a signal h to the turningbrake actuator means 3.

The operation of the first embodiment having the above-mentionedconfiguration will be described below.

In case the microprocessor 21 is working normally, if a turning leversignal a which is generated by the turning lever signal transmitter 1and which is a neutral position signal "1" is inputted to the input sideof the microprocessor 21, the microprocessor 21 will output a signal c,which is a normal signal "1", to the watchdog 23. As a result, thewatchdog 23 will also output a signal d which is a normal signal "1", sothat the microprocessor 21 is not reset. Thus, the microprocessor 21will output a signal b, which is representative of the result ofoperation by the microprocessor, to one input side of AND circuit 24. Atthat time, AND circuit 24 will receive at its another input side theoutput signal d (which is a normal signal "1") from the watchdog 23, sothat AND circuit 24 will output a signal f which is representative ofthe result of operation by the microprocessor 21.

Whilst, NOR circuit 25 will output a signal g which is an abnormalsignal "0", since the output signal d from the watchdog 23 is a normalsignal "1". As a result, OR circuit 26 will receive an output signal ffrom the AND circuit 24, i.e. the result of operation by themicroprocessor 21 and output a signal h so that the turning brakeactuator means 3 will be controlled in accordance with the result ofoperation by the microprocessor 21.

Next, the operation of the controlling system when the microprocessor 21mulfunctions will be described.

Since the output signal c from the micro-processor 21 is not a normalsignal "1" when the microprocessor 21 malfunctions, the watchdog 23 willoutput a signal d which is an abnormal signal "0". As a result, themicroprocessor 21 will be reset by the abnormal signal d. At that time,since an abnormal signal "0" form the watchdog 23 is input to one inputside of AND circuit 24, the latter will output a signal f which is anabnormal signal "0". Further, a turning lever signal "a" is thenoutputted by the turning lever signal transmitter 1. The turning leversignal a is delayed several seconds by the delay circuit 22 and isoutputted by the latter as a signal e. At that time, since the signal d,which is an abnormal signal "0", from the watchdog 23 is input to aninput side of NOR circuit 25, the latter will output or transmit asignal g (which is an inverted signal) corresponds to the output signale from the delay circuit 22.

At that time, since OR circuit 26 will receive, at its one input side, asignal f, which is an abnormal signal "0", from the AND circuit 24, theOR circuit 26 will invert the signal from the turning lever signaltransmitter 1 and output a signal h the transmission of which is delayedby several seconds by the delay circuit 22 Thus, the turning brakeactuator means 3 will be controlled in accordance with the invertedsignal h.

Subsequently, the second embodiment of the present invention will bedescribed with reference to FIGS. 2 and 4.

In FIG. 2, the components indicated by the same reference numerals andreference symbols as those used in FIG. 1 have the same functions, andtherefore the description thereof is omitted herein to avoid theduplication of explanation.

In FIG. 2, reference numeral 20 denotes a turning brake controllingsystem arranged in the same configuration as those of this sort ofconventional controlling systems and adapted, when a turning lever (notshown) is shifted from it turning position to its neutral position, toreceive a turning lever signal a transmitted by the turning lever signaltransmitter 1 and output or transmit a turning brake actuating signal tothe turning brake actuator means 3.

Reference numeral 5 denotes a F/V converter adapted to receive, as aninput thereof, a pulse signal i from a turning speed sensor 4 whichpicks up the rotation of a turning motor (not shown) for turning theupper turning body of a power shovel, not shown, and convert the pulsesignal i into a voltage corresponding to the frequency thereof so as tooutput a variable voltage signal j. Reference numeral 6 denotes areference voltage source or generator means adapted to generate areference voltage signal v for defining the minimum turning speed of theupper turning body.

The turning brake controlling system 20 in the second embodimentcomprises a turning brake signal transmitter 201 adapted to receive aturning lever signal a which is outputted by the turning lever signaltransmitter 1 and output a turning brake signal b a predetermined timeafter the turning lever is shifted from its turning position to itsneutral position; a comparator 202 adapted to receive, as inputsthereof, the variable voltage signal i from the above-mentioned F/Vconverter 5 and the reference signal voltage signal v from the referencevoltage generator means 6, compare these signals and output a comparisonsignal k, a NAND circuit 203 adapted to receive, as inputs thereof; thecomparison signal k and the turning lever signal a; and an AND circuit204 adapted to receive, as inputs thereof, a NAND signal l from NANDcircuit 203 and the turning brake signal b from the aforementionedturning brake signal transmitter 201, and output an AND signal h(turning brake actuating signal) to the turning brake actuator means 3in accordance with the signals l and b.

Next, the operation of the second embodiment having the above-mentionedconfiguration will be described.

The turning lever signal a transmitted by the turning lever signaltransmitter 1 is a binary signal which is either "0" or "1". Since thesignal a is "0" when the upper turning body of a power shovel, notshown, is turning, NAND circuit 203 will output a normal signal "1" as aNAND signal l, regardless of the nature of the comparison signal k fromthe comparator 202. Whilst, at that time, since the turning lever signala is an abnormal signal "0", the turning brake signal b transmitted bythe turning brake signal transmitter 201 will become a normal signal "1"which is a brake release signal. Thus, the AND circuit 204 will receivethe turning brake signal b and the NAND signal l, both of which are "1"and output a turning brake actuating signal h, which is a turning brakerelease signal "1", to the turning brake actuator means 3.

In the next place, the operation of this turning brake controllingsystem when the turning brake is actuated will be described withreference to the timing diagram as shown in FIG. 4.

When the turning lever signal a is changed from "0" to "1"; that is;when the turning lever, not shown, is shifted from its turning positionto its neutral position, the voltage signal j from the F/V converter 5will reduce in accordance with a reduction in the turning speed of theupper turning body. When the signal j becomes less than the referencevoltage signal v from the reference voltage generator means 6 a time t₂after the turning lever signal a has changed, the comparison signal kfrom the comparator 202 is changed from "0" to "1". The time t₂ at thattime is preset irrespective of a delay time t₁ for the turning brakesignal b from the turning brake signal transmitter 201.

When the comparison signal k becomes "1", both the signals a and k whichare inputted to NAND circuit 203 become "1", so that the NAND signal lbecomes "0", and hence the AND signal h from AND circuit 204 becomes "0"thereby rendering the turning brake actuator means 3 operative.

When the turning lever signal a is changed from "1" to "0", the turningbrake signal b, the NAND signal l, and the AND signal h are changed from"0" to "1" at the same time, thereby releasing the turning brake.

Further, in case the turning speed of the upper turning body is high;that is to say; the voltage signal j from the F/V converter is high, andwhen the turning lever is shifted to its neutral; position, a time t₃which passes until the voltage signal j becomes less than the referencevoltage signal v will become longer than the delay time t₁ for theturning brake signal b, as shown on the right side in FIG. 4. In thiscase, the time which passes from the shifting of the turning lever toits neutral position until the turning brake is actuated will becomelonger than the above-mentioned delay time t₁.

Further, if the turning brake signal b from the turning brake signaltransmitter 201 becomes "0" before the NAND signal l becomes "0", thenthe AND signal h becomes "0" thereby rendering the turning brakeoperative.

As mentioned hereinabove, when the turning lever is shifted from itsturning position to its neutral position and the turning speed of theupper turning body becomes less than a preset value, the turning brakeis actuated even if it occurs within the delay time for the turningbrake.

Next, the third embodiment of the present invention will be describedwith reference to FIGS. 3 and 5. Further, in this third embodiment, thesame components as those of the second embodiments as shown in FIG. 2are indicated by the same reference numerals and reference symbols, thedescription of them is omitted to avoid the duplication of explanation.

In FIG. 3, reference numeral 30 denotes a turning brake controllingsystem which is similar to the system 20 as shown in FIG. 2. The turningbrake controlling system 30 includes an integrator 301 adapted tointegrate a turning lever signal a which is outputted by a turning leversignal transmitter 1; a sample holding circuit 302 adapted, when itreceives the turning lever signal a; that is to say; the moment theturning lever is shifted from its turning position to its neutralposition, to hold a voltage signal j which is outputted by a F/Vconverter 5 in accordance with the turning speed of the upper turningbody at that time; a comparator 303 adapted to receive, as inputsthereof, a sample hold signal m which is outputted by the sample holdingcircuit 302 and a turning brake signal b' which is outputted by theintegrator 301, compare these signals and output a comparison signal n;and a NAND circuit 304 adapted to receive, as inputs thereof, theturning lever signal a and the comparison signal n and output a turningbrake actuating signal h to a turning brake actuator means 3 inaccordance with the signals a and n.

In the above-mentioned configuration, since the turning lever signal awhich is outputted when the upper turning body is turning is "0", NANDcircuit 304 will output a turning brake release signal, which is "1"irrespective of the comparison signal n from the comparator 302, to theturning brake actuator means 3.

Next, the operation of the system when the turning brake is actuatedwill be described with reference to the timing diagram as shown in FIG.5.

When the turning lever signal a is changed from "0" to "1"; that is tosay; a turning lever, not shown, is shifted from its turning position toits neutral position, the output of the integrator 301; that is to say;an integration signal b' will gradually change with time from "0" to"1". At that time, the sample holding circuit 302 will hold an output ofthe F/V converter when the turning lever signal a is changed from "0" to"1"; that is; a voltage which is proportional to the turning speed ofthe upper turning body when the turning lever is shifted from itsturning position to its neutral position, and output a sample holdsignal m accordingly. The comparator 303 serves to compare always theintegration signal b' with the sample hold signal m, and output acomparison signal n which is "1", when the output of the integrationsignal b' is increased and exceeds the voltage held by the sampleholding circuit 302 a time t₄ after the turning lever signal a ischanged from "0" to "1". Since the turning lever signal a is "1", theNAND signal h becomes "0" when the comparison signal n has become "1",and as a result, the turning lever actuator means 3 is renderedoperative.

As mentioned hereinabove, the turning brake actuator means is actuatedafter a delay time which corresponds to the turning speed of the upperturning body when the turning lever is shifted from its turning positionto its neutral position.

While the invention has been particularly shown and described inreference to preferred embodiments thereof, it will be understood bythose skilled in the art that changes in form and details may be madetherein without departing from the spirit and scope of the invention.

What is claimed is:
 1. A turning brake controlling system for use in anupper turning body of a power shovel, comprising:a microprocessor meansfor receiving a turning lever signal from a turning lever signaltransmitter when a turning lever is shifted from a turning portion to aneutral position thereof, and for transmitting a turning brake actuatingsignal to the turning brake actuator means; a microprocessor monitoringmeans operably connected to said microprocessor means for monitoring anoperation of said microprocessor means; a hardware circuit meansconnected in parallel with said microprocessor means for performingarithmetic functions of said microprocessor means; and a switchingcircuit means for switching output of said microprocessor means over toan output of said hardware circuit means in accordance with theactuation of said microprocessor monitoring means, wherein at least oneof said microprocessor means and hardware circuit means includes aturning speed detector means for detecting a turning speed of said upperturning body when said turning lever is shifted from said turningposition to said neutral position thereof and subsequent speeds thereof,and for outputting a turning speed signal corresponding to a detectedturning speed; and a turning brake signal generator means for receivingsaid turning speed signal outputted by said turning speed detector meansand said turning lever signal outputted by said turning lever signaltransmitter means and for outputting a turning brake signal to saidturning brake actuator means, and wherein said turning brake signalgenerator means is arranged to output a turning brake signal in a delaytime which is present in accordance with the value of said turning speedsignal.
 2. A turning brake controlling system for use in a power shovelas claimed in claim 1, wherein said turning brake signal generator meansoutputs a turning brake signal when said turning speed signal becomesless than a preset value.
 3. A turning brake controlling system for usein a power shovel as claimed in claim 2, wherein said turning speeddetector means includes a turning speed sensor means for detecting saidturning speed of said upper turning body of said power shovel and foroutputting a turning speed signal corresponding to said detected turningspeed, and a F/V converter means for receiving turning speed signal fromsaid sensor means and for converting said turning speed signal into avoltage signal to be outputted therefrom,said turning brake signalgenerator means includes: a turning brake signal transmitter means forreceiving said running lever signal outputted by said lever signaltransmitter and outputting a turning brake signal within a preset timeafter said turning lever is shifted from said turning position to saidneutral position thereof, a reference voltage generator means forgenerating a reference voltage signal for defining a minimum turningspeed of said upper turning body, a comparator for receiving saidvoltage signal from said F/V converter means and said reference voltagesignal for comparing voltage between said reference and F/V convertersignals, and for outputting a comparison signal, a NAND circuit meansfor receiving said comparison signal and said turning lever signal, andfor outputting a NAND signal, and an AND circuit means for receivingsaid NAND signal and said turning brake signal from said turning brakesignal transmitter means and for outputting an AND signal whichcorresponds to said NAND signals and turning brake signals to saidturning brake actuator means.
 4. A turning brake controlling system foruse in a power shovel as claimed in claim 1, wherein said turning speeddetector means includes:a turning speed sensor means for detecting saidturning speed of said upper turning body of said power shovel, and foroutputting a turning speed signal corresponding to said detected turningspeed, and a F/V converter for receiving said turning speed signal fromsaid sensor means, and for converting said turning speed signal into avoltage signal, and wherein said turning brake signal generator meansincludes: an integrator for integrating said turning lever signaloutputted by said turning lever signal transmitter means, and foroutputting an integration signal, a sample holding circuit means forreceiving said turning lever signal the moment said turning lever isshifted from said turning position to said neutral position thereof, andfor holding said voltage signal from said F/V converter means which isoutputted in accordance with said turning speed of said upper turningbody at that time, a comparator means for receiving sample hold signaloutputted by said sample holding circuit means and said integrationsignal outputted by said integrator means, for comparing between saidsample hold signal and integration signal, and for outputting acomparison signal, and a NAND circuit for receiving said turning leversignal and said comparison signal, and for outputting a NAND signalwhich corresponds to said turning lever signal and said comparisonsignal to said turning brake actuator means.